The Government has officially declared a state of drought in Northland.

Primary Industries Minister Nathan Guy said the weather in Northland was beyond "a normal dry summer", and had moved into an extreme climatic event.

"The entire North Island is extremely dry, but Northland is one of the worst-hit areas.

"The declaration of a medium-scale event means that extra Government funding will now be available to co-ordinate support through local organisations like the Rural Support Trusts.

In extreme cases there will also be Rural Assistance Payments (RAPs) available to farmers in severe hardship.

"This drought decision has been made after receiving advice from the Ministry for Primary Industries, including soil moisture data from Niwa, and in consultation with the local community. It applies to the area north of the Auckland Harbour Bridge.

"We are closely watching other parts of the North Island which are extremely dry, in particular the Waikato and Hawke's Bay."

Federated Farmers Northland provincial president Matt Long said the declaration was welcome news.

"It opens up a lot of avenues for farmers, and at the base of it, acknowledge that a problem exists."

Long said as well as advice and support farmers would be able to receive through Rural Support Trusts, concessions could be made available to those who were financially struggling.

"For example, it enables the IRD to have some flexibility toward tax payments. Taxes still have to be paid, but [the drought declaration] allows for more time to make those payments."

Long said a handful of farmers in Northland would almost certainly need to receive payments "similar to an unemployment benefit".

"The last big drought we had in 2010, there were about 20 farmers that needed the financial assistance, we're estimating this time there will be at least twice that."

A dry spring across most of the country meant silage stocks were down and shipping feed in from outside the region had become near impossible.

Long said he had also heard anecdotal evidence to suggest some inexperienced lifestyle block owners were rationing drinking water for cattle.

"It's worrying that this is happening. Farmers need to make available at least 60 litres of drinking water available per cattle per day."